Odontogenesis is a classic example of epithelial-mesenchymal signaling. In contrast to the bounty of information regarding the specification of early tooth development, little is know about the genes responsible for differences in tooth shape. This information is needed to understand the mechanisms behind vertebrate tooth diversity, the evolution of mammalian heterodonty, and the underlying cause of certain human dental disorders. There are no genetic knock-outs in mouse that recapitulate tooth shape phenotypes and other model organisms (zebrafish, frog, chick) either lack teeth in the oral jaws or exhibit radically derived dentitions. Here, a new system in which to study variance in tooth morphology is described. Labeotropheus fuelleborni (Lf) and Metriaclima zebra (Mz), two species of cichlid fishes from Lake Malawi, Africa have tricuspid and bicuspid teeth respectively. This proposal describes the identification of genomic regions associated with tooth shape differences in F2 fish derived from the inter-cross of Lf and Mz. The role of specific candidate genes is evaluated by mapping these loci in the same cross and by studying patterns of candidate gene expression in parental and hybrid embryos. These data will contribute to a molecular understanding of differences in vertebrate tooth shape.